1. Field of the Invention
The present invention relates to a dispensing apparatus for quantitatively dispensing blood, urine, etc. and particularly to a dispensing apparatus adapted for diluting and dispensing blood, urine, etc.
2. Description of the Related Art
In an automatically analyzing apparatus, analysis items in a vital sample such as blood, urine, etc. are analyzed by using a dispensing apparatus in such a manner as follows. The vital sample is dispensed into reaction containers on a reaction line. The sample is made to react with a reaction reagent in each of the reaction containers. A reaction solution produced as a result of the reaction is measured, for example, optically. In this manner, analysis items in the sample are analyzed. In the automatically analyzing apparatus, various reaction reagents are used in accordance with a large number of analysis items. To reduce the running cost of such inspection work, it is necessary to reduce the quantity of use of each reaction reagent.
To keep the range of measurement in the same concentration as obtained before the quantity of the reagent is reduced, the quantity of the sample needs to be reduced in the same rate as the quantity of the reagent is reduced. When, for example, the quantity of the reagent is reduced to half, the quantity of the sample is also reduced to half so that the concentration of the sample relative to the reagent is kept constant.
Two methods have been heretofore used for reducing the quantity of the sample. In one of the methods, the sample is diluted, while in the other of methods, the quantity of dispensation per se is reduced. The terminology xe2x80x9cdilutionxe2x80x9d will be described upon the case where the sample is diluted by 10 times by way of example. When 1 xcexcl of an undiluted sample is dispensed, 9 xcexcl of a diluting solution is added to the undiluted sample so that the undiluted sample is diluted by 10 times. That is, 10 xcexcl of a diluted sample solution is prepared. Out of 10 xcexcl, 2 xcexcl of the diluted sample solution is dispensed into each reaction container. (In this case, the dilution is equivalent to about 5-fold dilution.) On the other hand, in the method of reducing the quantity of dispensation per se, the minimum quantity of dispensation is limited to about 1 xcexcl. If the quantity is reduced to be smaller than about 1 xcexcl, reproducibility is lowered.
For example, as the background-art sample diluting method, a method disclosed in JP-A-11-230970 is known. In the method, a sample is sucked into a probe by a sample syringe while a diluting solution is made to flow by using a diluting syringe. Hence, both the suction and dilution of the sample are performed simultaneously. The diluted sample is delivered into each reaction container by using the sample syringe. In the method, the sample can be diluted without use of any dilution exclusive line. Hence, efficient dilution and dispensation can be made in a short time.
In the method described in JP-A-11-230970, it is, however, necessary that the size of the sample syringe is selected to be larger than the size of the diluting syringe. This is because the diluting syringe is required to feed out only a predetermined amount of the diluting solution, while the sample syringe is required to suck a predetermined amount of the sample in addition to the diluting solution fed out by the diluting syringe. Accordingly, the size (flow quantity) of the sample syringe becomes larger than that of the diluting syringe. The fact that the syringe becomes larger means that the plunger diameter of the syringe becomes larger. That is, it is necessary that the plunger diameter of the sample syringe is selected to be larger than that of the diluting syringe. If the plunger diameter becomes larger, the accuracy in the quantity of suction of the sample is worsened. Hence, there is a problem that the accuracy of the diluting rate is deteriorated.
An object of the present invention is to provide a dispensing apparatus in which a sample can be diluted in a short time and in which the accuracy of the diluting rate is improved.
(1) In order to achieve the above object, according to the present invention, there is provided a dispensing apparatus comprising: a diluting solution moving means for moving a diluting solution in a flow path in forward and reverse directions; a probe connected to the flow path through a junction and capable of sucking a sample; a sample syringe connected to the flow path through a junction; and a control means for controlling operations of the diluting solution moving means and the syringe, whereby the control means performs controlling so that the diluting solution moving means driven to move the diluting solution in the flow path and the syringe is driven to make the probe suck sample into the flow path to thereby dilute the sucked sample with the moved diluting solution, and the syringe is further driven so that the sample solution diluted with the diluting solution is delivered from the probe into a reaction container.
By such a configuration, the sample can be diluted in a short time and the accuracy of the diluting rate can be improved.
(2) In the above item (1), preferably, the above control means performs control so that the sample syringe is operated to deliver a high-concentration sample out of the probe into a washing bath before the diluted sample solution is discharged from the probe by the sample syringe.
(3) In the above item (1), preferably, the above control means performs control so that the sample syringe is operated to move the diluting solution in the flow path in a direction opposite to a direction of movement of the diluting solution at the time of dilution of the sample to thereby move the sample diffused in the flow path before the diluted sample solution is discharged from the probe by the sample syringe.
By such a configuration, diluting error can be reduced.
(4) In the above item (1), preferably, the diluting solution moving means includes: a first syringe connected to an end portion of the flow path; a second syringe connected to the other end portion of the flow path; and a drive means for driving plungers of the first and second syringes; wherein the first and second syringes operate so that the second syringe discharges the diluting solution in the flow path when the first syringe sucks the diluting solution in the flow path, and that the second syringe sucks the diluting solution in the flow path when the first syringe discharges the diluting solution in the flow path, the quantity of suction by the first syringe being equal to the quantity of delivery by the second syringe.
(5) In the above item (1), preferably, the above diluting solution moving means includes: a plurality of rollers for squashing a tube connected to opposite ends of the flow path; and a drive means for driving the rollers to rotate in forward and reverse directions.